Clutch with pressure sustaining system

Abstract

An assembly includes an output shaft, an input shaft with an internal reservoir, and a clutch. The clutch is adapted to selectively engage and couple the input shaft to the output shaft. The clutch has a pressure chamber that communicates with the reservoir of the input shaft. The reservoir has a sufficient volume to provide the pressure chamber with a fluid pressure adequate to maintain engagement of the clutch during an interruption of a fluid supply to the input shaft and clutch.

The invention claimed is: 
     
       1. An assembly comprising:
 an output shaft; 
 an input shaft having an internal reservoir; 
 a balance pressure chamber having a first fluid inner radius which is fixed during operation; and 
 a clutch adapted to selectively engage and couple the input shaft to the output shaft, the clutch comprising:
 an actuation pressure chamber that communicates with the reservoir of the input shaft, wherein the actuation pressure chamber has a second fluid inner radius which is variable during operation; and
 one or more passages that communicate fluid generally radially outward from the reservoir to the actuation pressure chamber, wherein the one or more passages include one or more axial bleed orifices connecting the one or more passages to a plenum axially overlapping with a plurality of clutch plates and radially between the clutch plates and the reservoir; and 
 wherein in operation during an interruption of a fluid supply to the input shaft the second fluid inner radius is located radially inward of the first fluid inner radius such that during the interruption of the fluid supply to the input shaft a centrifugal head pressure of the actuation pressure chamber is greater than a centrifugal head pressure of the balance pressure chamber, and wherein the reservoir has a sufficient volume to maintain the second fluid inner radius radially inward of the first fluid inner radius such that the actuation pressure chamber is provided with a fluid pressure adequate to maintain engagement of the clutch-during an interruption of a fluid supply to the input shaft. 
 
 
 
     
     
       2. The assembly of  claim 1 , wherein the one or more bleed orifices are sized to provide the actuation pressure chamber with a fluid pressure adequate to maintain engagement of the clutch during the interruption of fluid to the input shaft and clutch. 
     
     
       3. The assembly of  claim 1 , wherein one or more radial orifices connect the plenum to the reservoir. 
     
     
       4. The assembly of  claim 1 , wherein a duration of interruption is less than about 6 seconds. 
     
     
       5. The assembly of  claim 1 , wherein the clutch comprises a rotating transfer coupling that extends from and has portions integral with the input shaft. 
     
     
       6. The assembly of  claim 1 , wherein the clutch includes a piston that linearly moves to vary a size of the actuation pressure chamber in response to changes in fluid pressure. 
     
     
       7. The assembly of  claim 6 , wherein the piston acts as a pressure actuator to contact the clutch plates together to transfer torque from the input shaft to the output shaft. 
     
     
       8. An aircraft comprising:
 an airframe; 
 a drive system supported by the airframe, wherein the drive system comprises:
 an output shaft; 
 an input shaft having an internal reservoir; 
 a balance pressure chamber having a first fluid inner radius which is fixed during operation; and 
 a clutch adapted to selectively engage and couple the input shaft to the output shaft, the clutch comprising:
 an actuation pressure chamber that communicates with the reservoir of the input shaft, wherein the actuation pressure chamber has a second fluid inner radius which is variable during operation; and 
 one or more passages that communicate fluid generally radially outward from the reservoir to the actuation pressure chamber, wherein the one or more passages include one or more axial bleed orifices connecting the one or more passages to a plenum axially overlapping with a plurality of clutch plates and radially between the clutch plates and the reservoir; and 
 wherein in operation during an interruption of a fluid supply to the input shaft the second fluid inner radius is located radially inward of the first fluid inner radius such that during the interruption of the fluid supply to the input shaft a centrifugal head pressure of the actuation pressure chamber is greater than a centrifugal head pressure of the balance pressure chamber, and wherein the reservoir has a sufficient volume to maintain the second fluid inner radius radially inward of the first fluid inner radius such that the actuation pressure chamber is provided with a fluid pressure adequate to maintain engagement of the clutch during an interruption of a fluid supply to the input shaft. 
 
 
 
     
     
       9. The aircraft of  claim 8 , wherein the clutch includes one or more passages that communicate fluid from the reservoir to the actuation pressure chamber. 
     
     
       10. The aircraft of  claim 9 , wherein the one or more passages include one or more bleed orifices, and wherein the one or more bleed orifices are sized to provide the actuation pressure chamber with a fluid pressure adequate to maintain engagement of the clutch during an interruption of fluid to the input shaft and clutch. 
     
     
       11. The aircraft of  claim 10 , wherein one or more radial orifices connect the plenum to the reservoir. 
     
     
       12. The aircraft of  claim 8 , wherein the clutch comprises a rotating transfer coupling that extends from and has portions integral with the input shaft. 
     
     
       13. The aircraft of  claim 8 , wherein the aircraft comprises a high speed vertical takeoff and landing (VTOL) rotary-wing aircraft. 
     
     
       14. The aircraft of  claim 8 , wherein the drive system comprises a secondary thrust system. 
     
     
       15. The aircraft of  claim 8 , wherein the fluid supplied to the input shaft and clutch comes from a lubrication system of the aircraft. 
     
     
       16. An assembly comprising:
 an output shaft; 
 an input shaft having an internal reservoir; 
 a balance pressure chamber having a first fluid inner radius which is fixed during operation; and 
 a clutch adapted to selectively engage and couple the input shaft to the output shaft, the clutch having an actuation pressure chamber that communicates with the reservoir of the input shaft via one or more passages, wherein the one or more passages include one or more axial bleed orifices in fluid communication with a plenum axially overlapping with a plurality of clutch plates and radially between the clutch plates and the reservoir, wherein the actuation pressure chamber has a second fluid inner radius which is variable during operation, wherein in operation during an interruption of a fluid supply to the input shaft the second fluid inner radius is located radially inward of the first fluid inner radius, and wherein the one or more bleed orifices and the reservoir of the shaft are sized to maintain the second fluid inner radius radially inward of the first fluid inner radius such that the actuation pressure chamber has a fluid pressure adequate to maintain engagement of the clutch during the interruption of a fluid supply to the input shaft and clutch. 
 
     
     
       17. The assembly of  claim 16 , wherein the clutch comprises a rotating transfer coupling that extends from and has portions integral with the input shaft. 
     
     
       18. The assembly of  claim 16 , wherein the clutch includes piston slides to vary a size of the actuation pressure chamber in response to changes in fluid pressure. 
     
     
       19. The assembly of  claim 18 , wherein the piston acts as a pressure actuator to contact the clutch plates together to transfer torque from the input shaft to the output shaft. 
     
     
       20. The assembly of  claim 1 , wherein the balance pressure chamber is circumferentially open at an inner radial end.